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xylene isomers, chlorobenzene, 1,4-dichlorobenzene, 1,3- <br /> dichlorobenzene, and 1,2-dichlorobenzene. The latter analysis <br /> quantifies the heavier hydrocarbons and is expressed as a single <br /> concentration. This analytical suite is consistent with the work <br /> Performed on March 30, 1987. <br /> All samples of all ,compounds yielded nondetectable concentra- <br /> tions. Appendices A and B present the laboratory data sheets for <br /> each soil and water sample, respectively, and include internal <br /> laboratory quality assurance/quality control analyses. <br /> 6.0 Conclusionsand Recommendations <br /> With the completion of the scope of work as previously discussed, <br /> the primary findings can be summarized as follows: <br /> o The typical soil lithologies in the unsaturated zone at the <br /> site are predominantly silts and clays, a soil type charac- <br /> terized by moderate to low transmissivities; <br /> r. o The typical soil lithology in the saturated zone, - <br /> lady below 60 feet BGS, partic <br /> is sand, a soil type characterizeud <br /> by high transmissivities as demonstrated by the monitor well <br /> groundwater yield; <br /> o The previous analytical work at the site indicated little <br /> lateral spread of diesel residues near -the location of t <br /> excavated diesel tank; he <br /> o The previous analytical work at the site indicated an <br /> attenuation of diesel residues with increas;ng depth direct- <br /> ly below the location of the excavated diesel tank, and; <br /> o The recent analytical work did not find any detectable <br /> concentrations of compounds present in d esel fim-- in either <br /> the soil or groundwater at the site. <br /> w it should be noted that any leakage of diesel fuel from the <br /> underground tank had to have occurred no later than June 26, <br /> 1986, when the tank was removed. Therefore, at least two years <br /> have elapsed since the tank could have relaased any fuel. Given <br /> that the downgradient well is located approximately loo feet away <br /> from the excavated soils and that the shallow aquifer appears to <br /> be of moderate to high transmissivity, diesel fuel products <br /> should be observable by now if the diesel--leakage—had.-_impacted <br /> ------------groundwater-qua -._-- --�- <br /> q y_.___In actuality, the recent analytical results <br /> show the siteto be free of diesel residues in the groundwater. <br /> Therefore, WESTON do <br /> site. es not recommend any additional work at the <br /> 6 - <br />